Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$22.92	10.870%	$25.4114	$25.41	$25.40	$25.40
Purchase #2	$145.88	3.820%	$151.4526	$151.45	$151.45	$151.50
Purchase #3	$103.36	9.589%	$113.2712	$113.27	$113.25	$113.30
Purchase #4	$70.79	13.214%	$80.1442	$80.14	$80.15	$80.10
Purchase #5	$214.80	4.549%	$224.5713	$224.57	$224.55	$224.60
Purchase #6	$61.32	12.302%	$68.8636	$68.86	$68.85	$68.90
Purchase #7	$88.78	12.211%	$99.6209	$99.62	$99.60	$99.60
7 purchase totals =	$707.85		$763.3352	$763.32	$763.25	$763.40